Yeah, I tried that, but couldn't find a backend that would work seamlessly. And besides, it still can't do the transcoding/mobile app stuff Plex can.
I love the customisability of Kodi but there's something to be said for a front-to-back, opinionated solution. It works a lot better (...even though my original complaint is that Plex can be flaky...)
The reason I pointed out Emby is that it has all the features Plex does that Kodi does not. Kodi has some stuff available by plugin but matching the features I require from Plex has never been possible.